Study of Dalantercept in Patients With Squamous Cell Carcinoma of the Head and Neck

Key Inclusion Criteria: * Histologically and/or cytologically confirmed, recurrent or metastatic SCCHN of mucosal origin (oral cavity, oropharynx, hypopharynx or larynx) not amenable to further local therapy (surgery, or radiation including re-irradiation); patients with unknown primary SCCHN presumed to be of head and neck mucosal origin are eligible if they meet all other entry criteria. * Previously treated with at least one platinum-containing regimen or contraindicated for treatment with a platinum containing therapy. (Note: platinum therapy can occur upfront or after recurrence of disease. Failure of platinum therapy is not required.) * Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1. Key Exclusion Criteria: * Nasopharyngeal carcinoma, paranasal sinus, salivary gland or primary skin SCCHN. * Any other active malignancy for which chemotherapy or other anti-cancer therapy is indicated. * Chemotherapy or other anti-cancer therapy or radiation therapy within 5 times the half-life of the drug or within 3 weeks prior to study day 1 if the half-life is not known. * Treatment with another investigational drug or device, or approved therapy for investigational use, within 5 times the half-life of the drug or within 3 weeks prior to study day 1 if the half-life is not known. * Major surgery within 4 weeks prior to study day 1 (patients must have recovered completely from any previous surgery prior to study day 1). * Clinically significant cardiovascular risk. * Clinically significant active pulmonary risk. * Clinically significant active bleeding. * Peripheral edema ≥ Grade 1 within 4 weeks prior to study day 1. * Pregnant or lactating female patients.